Preheat the oven to 200°C / fan 180°C / gas 6. Bring a pan of water to the boil and cook the potatoes for 10 minutes until tender. Drain thoroughly, then toss with the 2 tbsp of the olive oil, thyme and 3 cloves of the garlic, which should be lightly bashed beforehand. Season, then put in a roasting tin and cook in the oven for 30-35 minutes, shaking the tray occasionally.
Meanwhile, heat the remaining oil in a large, lidded saucepan or casserole dish, and add the shallots. Cook for 2-3 minutes until beginning to soften. Crush the remaining garlic clove, then add to the onion and cook for another minute.
Add the chicken and cook for 4-5 minutes, turning using a pair of tongs to turn until brown all over.
Pour in the cider and bubble for a minute, before adding the stock. Cover with the lid and simmer for 30 minutes. Remove the lid and cook for another 12-15 minutes until the sauce has reduced slightly, and the chicken is tender and cooked through. Finally, stir through the crème fraiche and mustard and finish with a scattering of parsley. Keep warm.
Add the green beans to a pan of boiling water just before serving and cook for 3-4 minutes. Drain thoroughly.
Serve the chicken with the green beans and potatoes on the side.